Mechanical saturable reactor



Nov. 16, 1965 A. E. FLANDERS ETAL 3,213,545

MECHANICAL SATURABLE REACTOR 3 Sheets-Sheet 1 Filed Nov. 16. 1961INVENTORS ANDREW E. FLANDERS 8:

JOSEPH MONTNER ATTORNEY Nov. 16, 1965 A. E. FLANDERS ETAL 3,213,545

MECHANICAL SATURABLE REACTQR Filed Nov. 16, 1961 3 Sheets-Sheet 3INVENTORS ANDREW E. FLANDERS a JOSEPH MONTNER BY 9 a.

A RNEY United States Patent 3,218,545 MECHANICAL SATURABLE REACTORAndrew E. Flanders, 257 Hickory Ave., Pomona, Calif., and i losepl1Montner, 9242 Andasol Ave., Northridge, Cali Filed Nov. 16, 1961, Ser.No. 152,865 8 Claims. (Cl. 323-90) This application is acontinuation-in-part of application Serial No. 639,332, filed February11, 1957, now abandoned, similarly entitled, and assigned to theassignee of this application.

This invention relates generally to mechanical saturable reactors foruse in electrical signal control or as electromechanical transducers;more particularly, it relates to a mechanical saturable reactor whereinan output voltage is varied according to the rotational position of arotor.

Heretofore, various electromechanical and other transducers, togetherwith their associated amplifiers, have generally been used to drive thecontrol windings of conventional saturable reactors. Rheostats andvariable autotransformers have also been used to control the powerdelivered to a load. Such devices introduce contact and resolutionproblems. Variable auto-transformers produce shorted-turn circulatingcurrents.

Circuit control devices of the prior art have also employed slidingelectrical contacts, which are characterized by such contact problems asnoise, sparking, pitting, wear, and chatter under adverse environmentalconditions. In electromechanical transducer applications, mechanicalmovements have been detected by various types of transducers, includingotentiometers, and the responsive electrical voltage is fed to a grid ofa vacuum tube. As is well known, vacuum tubes introduce a highprobability of failure. Conventional wire wound or carbon potentiometersand inductive potentiometers do not of themselves provide high poweroutput or wide power range.

In contrast with the prior art, the mechanical saturable reactor of thepresent invention inherently provides wide power range. It does notnecessarily require vacuum tubes or similar amplifying components. It isnot subject to contact and resolution problems and does not haveshorted-turn circulating currents. It does not require the use ofrheostats or transformers in delivering power to a load, but delivers itdirectly to the load.

Saturable reactors of the prior art used for voltage control haveemployed controllable D.C. sources for varying the magnetization ofcores around which are disposed coils connecting an AC. source to itsload. In the case of the present invention, control is accomplishedmechanically and no D.C. source nor means for varying D.C. controlcurrent is required.

It is therefore an object of the present invention to provide animproved saturable reactor which does not require a variable D.C.magnetization source.

It is an object of the present invention to provide a circuit controldevice which is free of problems associated with sliding electricalcontacts, such as noise, sparking, pitting, poor resolution, and wear.

It is an object of this invention to provide a mechanical saturablereactor wherein mechanical movement is translated directly into usefulelectrical output.

It is another object of the present invention to provide a mechanicalsaturable reactor :having linear and nonlinear response for selectiveoperation.

It is another object of this invention to provide a mechanical reactorwherein the effective core cross-sectional area of a magnet core and thesaturation flux density therein are selectively variable and control auseful electrical output.

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It is a further object of this invention to provide a sensitive circuitcontrol device of simple design, which is composed entirely of passiveelements; which occupies a minimum of space, and which is inexpensive tofabricate.

It is a further object of the present invention to provide a mechanicalsaturable reactor which is dependable and relatively trouble-free underadverse service conditions.

Other objects and features of the present invention will become apparentto those skilled in the art from a con sideration of the followingdescription, the appended claims, and the accompanying drawings inwhich:

FIGURE 1 is a perspective view of a preferred embodiment of a mechanicalsaturable reactor according to the present invention;

FIGURE 2 is a perspective view, partially in section, of a modifiedmechanical saturable reactor according to the present invention;

FIGURE 3 is a perspective view, partially in section, of a thirdembodiment of the present invention;

FIGURE 4 is a graphical representation showing core magnetization as afunction of magnetizing force under certain conditions;

FIGURE 5 is a graphical representation showing certain load voltages asfunction of the angular disposition of the rotor of a mechanicalsaturable reactor of this invention;

FIGURE 6 is a schematic diagram of the electrical circuitry of theembodiment of the present invention shown in FIGURE 1; and

FIGURES 7 and 8 are schematic diagrams showing exemplary circuits withwhich the device of the present invention may be utilized.

Referring to the drawings, a preferred embodiment of the presentinvention is shown in FIGURE 1 as including a coil or winding 11 woundin conventional manner around a generally C-shaped core member 12 ofmagnetizable material, confronting pole portions 13 and 14 of whichdefine a nonmagnetic gap. The end portions of the nonmagnetic gap,defined by parallel confronting faces of pole portions 13 and 14, areoccupied by nonmagnetic spacers 16 and 17, as shown. The central majorportion of the nonmagnetic gap has a generally circular configurationdefined by curved surfaces 18 and 19 of pole portions 13 and 14.Magnetic rotor 21, having a cylindrical configuration complemental withthis circular gap configuration, is mounted on shaft 22 for rotation inthe gap. AC. voltage is applied across coil 11 by generator 23 toproduce magnetic flux in core 12. Shaft 22 may be rotated manually or itmay be rotated continuously by motor 25. The rotational position ofshaft 22 may be made responsive to an external mechanical position ormovement for control or measurement purposes.

In the embodiment shown in FIGURE 1, rotor 21 is preferably constructedof anisotropic material. The material may be one of the grain-orientediron alloys known by such trade names as Silectron, Hipersil, Trancor,Corosil, Deltamax, Permeron, Permenorm, Orthonol, or Orthonik. Thismaterial may be of the type disclosed in the patents to Holst et al.,Number 2,147,791, issued February 21, 1939 and to Bitter, Number2,046,717, issued July 7, 1936. The magnetization characteristics ofsuch materials vary with angular position in a magnetic path. For agiven magnetizing force, a rotor of such material will accommodate orhold differing maximum amounts of flux depending upon its rotationalposition. The flux density required to saturate the rotor magneticallywill thus vary with angular displacement. The graphical representationof FIGURE 4 shows magnetization curves for different angles of rotation.For example, at zero degrees, herein defined as the rotor position whichplaces the direction of greatest magnetization of rotor 21 in alignmentwith the magnetic path through the core and the nonmagnetic gap, a fluxdensity of more than 15 kilogauss is produced by a magnetizing force of1.0 oersted. At a position 20 removed from the direction of greatestmagnetization, a flux density of approximately 13 kilogauss is producedby the same magnetizing force, and at 45, the flux density with the samemagnetizing force is only 10 kilogauss.

Rotation of rotor 21 varies the effective cross-sectional area of themetallic magnetic path for the magnetic flux produced in core 12. Thatis, with the anisotropic material so oriented that the direction ofgreatest magnetization of the rotor is aligned with the magnetic paththrough the core, the effective cross-sectional area for magneticconduction is the greatest. As rotor 12 is rotated from this zeroposition, the effective cross-sectional area is progressively reduceduntil the anisotropic material is oriented approximately 45 to 90 fromthe position of maximum magnetization.

Rotation of rotor 21 varies the voltage across winding 11. This voltage,which is the voltage the coil can hold or absorb, is governed by thebasic relation where E is the RMS voltage across winding or inductor 11,F is the frequency of the AC. line voltage, N is the number of turns ofwinding 11, A is the effective crosssectional area of rotor 21, and B isthe flux density in core 12.

Reduction of the effective cross-sectional area of the core or rotor andconsequent reduction of flux density in core 12 reduces the voltageacross coil 11. Rotation of rotor 21 changes its effectivecross-sectional area, producing changes in the flux in the core. Whenthe rotor is in its zero" position, as hereinbefore defined, it presentsmaximum effective cross-sectional area to flux in core 12 and exhibitsmaximum flux density capacity; hence, the voltage across coil 11 will begreatest. As rotor 21 is rotated from this position, the effectivecross-sectional area of the core is progressively reduced and the fluxdensity in core 12 is accordingly reduced. The voltage across coil 11 isthereby reduced, in accordance with the above equation. It is assumed inthe foregoing discussion that the magnetizing force (in oersteds) isconstant throughout rotation of rotor 21.

In the circuit shown in FIGURE 6, where coil 11 is serially connectedbetween generator 23 and load 24, changes in voltage across coil 11produce inverse changes in the voltage across load 24, because the loadvoltage represents the difference between the generator voltage and thevoltages held or absorbed by the coil. FIGURE 5 shows the voltage 15,,across load 24 as a function of the angle of rotation of rotor 21.Voltage E is determined by three factors, the angular position of rotor21, the low flux density permeability of core 12 and rotor 21, and thesmall air gap between core and rotor. In FIGURE 5, E the voltage dropacross load 24, represents the summation of the curves reresented by Eand E E represents the voltage output across the load as a function ofthe angle of rotation of rotor 21, as developed from the B-Hmagnetization curve relationships shown in FIGURE 4. E represents thecombined effect of the small air gap and low fiux density permeability.With a uniform air gap a certain maximum inductive reactance isestablished, and thus a finite minimum output voltage appears at theload. Because the low level flux density permeability varies slightlywith changing angle, the E curve is shown with a slight slope.

By way of example, and not by way of limitation, the Curve E of FIGUREspecifically represents the voltage across a load of 60 ohms produced bya saturable reactor (the B-H curves of which are shown in FIGURE 4)connected to a 100 volt, 60 cycle, AC. voltage source. It is obviousthat the minimum and maximum amplitudes of this curve and its slope atdifferent points are matters of design and that they will vary accordingto such design factors as the particular reactor material selected andthe circuit components utilized. As shown in FIG- URE 5, load voltage Edecreases from 120 to 180 (60 to 0") of rotor rotation and increasesfrom 0 to 60 of rotation. Although not shown in FIGURE 5, this voltagedrops somewhat between 60 and of rotation and increases from 90 todeclining again from to of rotation, all in accordance with themagnetization curves of FIGURE 4.

Referring to FIGURE 2 of the drawings, there is shown a secondembodiment of the present invention wherein 2 rotors 21 and 21a aremounted on a common shaft 22. Rotor 21 is disposed in the nonmagneticgap defined by a first magnetic core 12, and rotor 21a iscorrespondingly disposed in the nonmagnetic gap defined by a secondmagnetic core 12a. The rotors are angularly so disposed with relation toeach other on shaft 22 that their respective direction of maximummagnetization are disposed at a relative angle of somewhat less than 90.Dual electrical outputs may be produced. In order to minimize thereluctance of the nonmagnetic gaps between rotors and cores, the spacesbetween the rotors and the pole portions of the cores may be filled withpowdered iron lubricated with silicon oil. In order to retain the fluidwithin the air gaps and within the device shown in FIGURE 2, a slightlycupped pressure plate 29, constructed of nylon or Teflon, is employed.

Referring to FIGURE 3, there is shown a third embodiment of themechanical saturable reactor of the present invention, wherein a rotor21b has the configuration of a frustrum of a cone and wherein a cam 31is mounted with rotor 21!) on shaft 22, as shown, so that it rides overprojection 32 on frame 33. The nonmagnetic gap defined by core 12 has aconfiguration adapted to accommodate rotor 21b. This configurationfacilitates reduction of the air gap between core 12 and rotor 21b bypermitting the rotor to seat in the pole portions of core 12. Thisminimizes the reluctance between core and rotor. Cam 31 provides meansfor axial movement of rotor 21b simultaneously with its rotation. Theaxial movement permits linear insertion or withdrawal of the rotor intoor out of the nonmagnetic gap of core 12. Obviously, the rate ofwithdrawal in relation to rotational speed is a matter of design. Itwill be observed that in the case of this embodiment both the effectivecross-sectional area and the actual physical cross-sectional area of therotor in the gap may be varied to vary the value of A in the basicequation hereinbefore set forth. By varying the rate of withdrawal orinsertion of rotor 21b from or into the nonmagnetic gap and bysimultaneously varying the rotational position of rotor 21b, the curverepresenting load voltage as a function of rotational position of therotor may be made linear or nonlinear depending upon the design of cam31. Curve E in FIGURE 5 represents such a linear curve and is producedby linear withdrawal of the rotor from the core. Curve E represents thevoltage across the load which is produced by simultaneous rotorwithdrawal and orientation change when an air gap of 1 mil or less wasvaried only slightly by means of cam 31.

FIGURES 7 and 8 show illustrative circuit arrangements for controlcircuitry with which the mechanical saturable reactor of the presentinvention may be utilized.

In FIGURE 7 the output voltage from the saturable reactor is rectifiedthrough D.C. bridge 26 to provide bias for magnetic amplifier 27 whichsupplies voltage to load 24. In FIGURE 8 energy source 23 excites thedivergent balanced network to provide a positive or negative D.C. outputbetween terminals 35 and 36 or to provide a push-pull D.C. output atterminals 34, 35, and 36. The embodiment of the present invention shownin FIGURE 2 is adapted for use in this circuit. The

'output supplied to one mixing resistor will increase with one directionof rotation while the output to the other mixing resistor will decrease.The net effect is increased voltage output of one polarity with rotationin a given direction. Upon rotation in the opposite direction, adecrease in output of the original polarity or an increase in output ofthe opposite polarity occurs. In this embodiment, nonmagnetic spacers 28are provided in order properly to constrain the flux in cores 12 and12a.

Those versed in the art will realize that the mechanical saturablereactor of the present invention is adapted for many diversified anduseful applications. For example, as shown schematically in FIGURE 1, itis adapted for use in connection with a high power acoustical warningdevice (siren). A high frequency carrier voltage is supplied to the coil11 of a saturable reactor, the coil being in series with speaker 37, androtor 21 is rotated continuously by motor 25 to modulate the output tothe speaker. A simple direct device having very few components is thusprovided. The device of the present invention is also adapted tofunction as an electromechanical transducer to provide linear ornonlinear outputs or combinations of both. It may be used for tuning aninductor over a narrow range or, with proper filtering, it may beutilized in the production of musical tones.

While certain .preferred embodiments of the invention have beenspecifically disclosed, it is understood that the invention is notlimited thereto as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims:

What we claim is:

1. A mechanical saturable reactor comprising an electromagnetic corehaving a pair of confronting pole portions defining a constant air gap,a coil wound around said core, a rotor of grain-oriented anisotropicmaterial having a rectangular hysteresis loop which will saturate indifferent angular positions mounted for rotation Within said air gap,said rotor having a circular configuration, means for increasing thepermeability of the Portion of said air gap not occupied by said rotorcomprising small magnetic particles and silicon oil within said gap, andsealing means for retaining said particles and said oil within said gap.

2. In an alternating voltage circuit having an alternating voltagesource and electrical means connected across said source constituting aload, a voltage control device comprising a core of magnetizablematerial having a pair of pole portions defining a constant nonmagneticgap, a rotor of rectangular hysteresis loop magnetic material havingpreferred directions of magnetization positioned within said air gap andcomplemental therewith, whereby said rotor will saturate in differentangular positions, a coil wound around said core and connected incircuit with said alternating voltage source and said load, the numberof turns of said coil being such as to produce rotor saturation duringeach half cycle of the alternating voltage, and means for turning saidrotor to determine the instant during each such half cycle at which saidrotor becomes saturated to govern the voltage maintained across saidwinding.

3. For use in an alternating voltage circuit having an alternatingvoltage source and electrical means connected across said sourceconstituting a load, a voltage control device comprising a circularlyshaped rotor having preferred directions of magnetization, whereby itwill saturate in different angular positions, a core of magnetizablematerial having pole portions defining a constant air gap, said poleportions having curved confronting surfaces corresponding with the shapeof said rotor, a coil wound around said core and connected in circuitwith said alternating voltage source and said load, the number of turnsof said coil being so related to the alternating voltage frequency as toproduce rotor saturation during each half cycle of the alternatingvoltage, and means for turning said rotor to determine the instantduring each such half cycle at which said rotor becomes saturated togovern the voltage drop across said winding.

4. For use in an alternating voltage circuit having an alternatingvoltage source and electrical means connected across said sourceconstituting a load, a voltage control device comprising a core ofmagnetically saturable material having a constant air gap therein, acylindrical element of magnetic material having preferred directions ofmagnetization supported within said air gap for rotational movement,whereby it will saturate in different angular positions, an alternatingvoltage winding wound around said core and connected in circuit withsaid alternating voltage source and said load, the number of turns ofsaid coil being such as to produce rotor saturation during each halfcycle of the alternating voltage, and mechanical means for selectiverotational positioning of said element to determine the instant duringeach half cycle of the alternating voltage where the rotor becomesmagnetically saturated to control the voltage maintained across saidwinding in accordance with the basic relation 1.4 lE=21rFNAB X10- whereE is the RMS equivalent of the average voltage across said Winding, F isthe frequency of the alternating voltage, N is said number of coilturns, A is the effective cross-sectional area of said element, and B isthe flux density in said core.

5. For use in an alternating voltage circuit having a voltage source andelectrical means connected across said source constituting a load, avoltage control device comprising a core of magnetic material having anair gap therein, a member of magnetic material having preferreddirections of magnetization supported for rotation within said air gapand arranged for translational movement with respect thereto, analternating voltage winding wound around said core and connected incircuit with said voltage source and said load, means for rotating saidmember to produce voltage variations across said Winding, and means forproducing translational displacement of said member to modify saidvoltage variations.

6. For use in an alternating voltage circuit having a voltage source andelectrical means connected across said source constituting a load, avoltage control device comprising a core of magnetic material having anair gap therein, a member of magnetic material having preferreddirections of magnetization supported for rotation within said air gapand arranged for translational movement with respect thereto, analternating voltage winding wound around said core and connected incircuit with said voltage source and said load, means for rotating saidmember to produce voltage variations across said Winding, and means foreffecting linear voltage variations by predetermined translationaldisplacements of said member.

7. A high power acoustical generating system comprising a high frequencycarrier source, a speaker, and a mechanical saturable reactor seriallyconnected thereto, said reactor comprising a magnetic core having poleportions defining an air gap, a coil wound around said core, a rotor ofanisotropic material saturable in different angular positions andmounted for rotation within said air gap, and means for continuallyrotating said rotor.

8. A mechanical saturable reactor comprising a first magnetic corehaving pole portions defining a first air gap, a first coil wound aroundsaid first core, a first rotor of anisotropic material Within said firstair gap, a second magnetic core having pole portions defining a secondair gap, a second coil wound around said second core, a second rotor ofanisotropic material within said second air gap, said second core beingso positioned relative to said first core that both said rotors are inaxial alignment, a common shaft connecting said rotors for rotationalmovement, and nonmagnetic spacers between said cores, coils and rotorsto constrain flux in said first core and in said second core.

(References on following page) References Cited by the Examiner UNITEDSTATES PATENTS Thomson 336-135 X Hellmund 323-90 X Clough 323-89 Bitter148-111 Bozorth et a1. 148-120 Wilkinson 340-384 Candy 336-135 8 6/1951Scharschu 336-218 X 4/1954 Schwig 323-89 10/1956 Side 336-135 X 10/1957Akeley 310-162 9/ 1959 Bozorth 336-218 FOREIGN PATENTS 5/ 1941 Germany.

LLOYD MCCOLLUM, Primary Examiner.

2. IN AN ALTERNATING VOLTAGE CIRCUIT HAVING AN ALTERNATING VOLTAGESOURCE AND ELECTRICAL MEANS CONNECTED ACROSS SAID SOURCE CONSTITUTING ALOAD, A VOLTAGE CONTROL DEVICE COMPRISING A CORE OF MAGNETIZABLEMATERIAL HAVING A PAIR OF POLE PORTIONS DEFINING A CONSTANT NONMAGNETICGAP, A ROTOR OF RECTANGULAR HYSTERESIS LOOP MAGNETIC MATERIAL HAVINGPREFERRED DIRECTIONS OF MAGNETIZATION POSITIONED WITHIN SAID AIR GAP ANDCOMPLEMENTAL THEREWITH, WHEREBY SAID ROTOR WILL SATURATE IN DIFFERENTANGULAR POSITIONS, A COIL WOUND AROUND SAID CORE AND CONNECTED INCIRCUIT WITH SAID ALTERNATING VOLTAGE SOURCE AND SAID LOAD, THE NUMBEROF TURNS OF SAID COIL BEING SUCH AS TO PRODUCE ROTOR SATURATION DURINGEACH HALF CYCLE OF THE ALTERNATING VOLTAGE, AND MEANS FOR TURNING SAIDROTOR TO DETERMINE THE INSTANT DURING EACH SUCH HALF CYCLE AT WHICH SAIDROTOR BECOMES SATURATED TO GOVERN THE VOLTAGE MAINTAINED ACROSS SAIDWINDING.